This invention relates to a portable machine tool and in particular to a portable flange facer.
Many industrial plants have systems of interconnected pipes for conducting gases and liquids. In many situations, two pipes are connected together by flanges, or a pipe may be connected to a vessel by a flange. The face of a flange may be subject to deterioration or other damage, and in order to prevent leakage caused by such deterioration, it is necessary to repair the flange by re-facing or re-grooving. This may be accomplished by depositing metal on the damaged flange and then machining the metal partially to leave a satisfactory surface. It may be inconvenient to remove a large pipe from the pipe system in which it is installed in order that it may be taken to a machine shop for repairing, and as a result, portable flange facers have been developed to perform the refacing and re-grooving in the field.
U.S. Pat. No. 4,852,435 discloses a portable flange facer that comprises a chuck that is fitted inside the bore of the pipe whose flange is being repaired and a machine body that is clear of the pipe when the chuck is mounted. A motor that is effective between the chuck and the machine body causes the machine body to rotate relative to the chuck. A tool bar extends through the machine body and carries a tool head. The tool bar is fed lengthwise as the machine body rotates.
In a portable flange facer, it may be desirable to be able to reverse the direction of feed of the tool head, e.g. from inward feed to outward feed. In the flange facer shown in U.S. Pat. No. 4,852,435, the feed direction can be reversed by demounting a feed slave unit from the machine body and reinstalling it in an inverted orientation. Naturally, this necessitates that rotation of the machine body be stopped. At times it would be more convenient if the feed direction could be reversed without its being necessary to stop rotation of the machine body, but in this case safety considerations dictate that the control member for accomplishing the reversal not be mounted on the machine body.
Many machine tools employ pneumatic drive motors. In a pneumatic drive motor, compressed air is supplied to the motor and is exhausted into the ambient atmosphere through a rather small port. This localized sudden reduction in pressure generates a substantial level of noise.